1. Field of the Invention
The invention relates generally to electrical switches of the reset type commonly used in safety applications where the normally closed position of the switch is forced to a normally opened position when an unsafe condition is sensed. The switch is then required to be reset to the normally closed position by application of manual force. The present invention relates particularly to such a switch with means for controlling the snap over force of the movable conductive blade, or snap spring, therein.
2. Description of the Prior Art
Snap switches utilized as reset switches are generally well known in the art. Switches which do not return to the normally closed position when actuated to the normally open position with the reset plunger held depressed, or nonrecycling switches, which need to be manually reset are also generally known in the art. One variety of these switches has an anchor member which controls the position of the conductive blade, or snap spring, which moves between a conductive pole and nonconductive pole or the normally closed and normally open positions, respectively. The anchor is attached to the snap spring by means of a bowed portion of the snap spring thereby determining the middle, or snap over, position of the conductive member. That is, when the conductive blade is in the normally closed position, if it is forced over its center position by an activating plunger it will snap over and continue until its conductive pad is placed on the nonconductive pole. The conductive pad then remains there in the normally open position. A reset plunger is then required to be pressed manually, or with outside force, in order to push the conductive blade back over the center position where it snaps back into the normally closed position with its conductive pad resting on the conductive pole so that the circuit is again connected. When the conducting blade snaps from the nonconductive pole to the conductive pole, considerable force is required. If the internal parts of the switch i.e. the anchor, and the bowed spring portion, are positioned too low, or towards the conductive pole, recycling, or bounce back of the switch to the normally closed position results in unwanted current flow through the switch. If the internal parts are positioned too high there may be insufficient force generated by the reset plunger to return the snap spring to the conductive pole.
There is therefore a need for a mechanism for controlling the force of snap over, or movement, of the conductive blade when it moves between the normally closed and normally opened positions.